Method of making high definition chevron type MR sensor

ABSTRACT

A method is provided for making a well-defined, highly-predictable chevron type MR sensor for a read head. A first material is selected for a first gap layer. A selected second material is deposited on the first gap layer followed by a resist frame that has elongated openings exposing elongated top portions of the first gap layer that extend at an acute angle to a head surface of the read head. A selected reactive ion etch (RIE) is employed to etch away the exposed portions of the second material layer down to the first material of the first gap layer. The material of the second material layer is chosen to be etched by the RIE while the material of the first gap layer is chosen not to be etched by the RIE. An example is Al 2 O 3  for the first gap layer, SiO 2  for the second material layer and a RIE that is fluorine based. The resist frame is removed leaving elongated strips of the second material layer extending at the aforementioned angle to the head surface. MR material is then sputtered on top of the first gap layer and on the second material strips building up a MR sensor which has a ribbed structure on each of its first and second surfaces. The resultant MR head has second material strips sandwiched between the first gap layer and the MR sensor.

CROSS REFERENCE TO RELATED APPLICATION

This is a divisional application of application Ser. No. 08/926,264filed Sep. 5, 1997, now U.S. Pat. No. 6,118,623.

This application is related to commonly assigned U.S. Pat. No. 5,530,608which is incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of making a high definitionchevron type magnetoresistive (“MR”) sensor, and more particularly to amethod of sputtering a chevron shaped MR sensor with high depth control,with planar walls that meet at 90°, and with no fencing upon removal ofa patterning mask.

2. Description of the Related Art

An MR read head is employed for sensing magnetic fields on a magneticstorage medium, such as a longitudinally moving magnetic tape of a tapedrive. In such a tape drive, the MR head is mounted on a support, whileguide rollers bias the tape into contact with a head surface of the readhead. When the tape moves longitudinally, the read head senses magneticfields in longitudinally extending tracks on the magnetic tape. Anactuator is connected to the support for moving the read headtransversely across the tape, to selected information tracks. A writehead is typically combined with a magnetoresistive (MR) read head toform a combined or merged MR head. With this arrangement the merged MRhead is also capable of writing information signals on selectedlongitudinally extending tracks as positioned by the actuator. Typicallythe write head writes tracks at a certain width, while the read headreads a narrower track width. In the art this is referred to as“write-wide, read-narrow”.

An MR head has an MR sensor sandwiched between first and second gaplayers that, in turn, are sandwiched between first and second shieldlayers. The MR sensor includes multiple thin film layers. The mostimportant layer is an MR stripe; the other layers are for biasing andcapping. The spacing between the first and second shield layersdetermines the linear read resolution of the MR head with respect to aninformation track. The MR stripe, which may be NiFe, is typicallyelongated, with its length aligned parallel to the head surface andperpendicular to the movement of the tape. By shape anisotropy thiselongation establishes an easy magnetic axis along the length of the MRstripe. Thus, without some biasing scheme, the magnetic moment of the MRstripe will be directed along its lengthwise direction.

First and second leads may be connected to opposite lengthwise ends ofthe MR sensor for conducting a sense current through the MR stripe. Thespacing between the leads establishes the active region of the MRsensor, which defines the sensor's track width. Sense current isprovided by channel electronics, which may also be referred to asprocessing circuitry. When sense current is conducted through the MRstripe, resistance changes in the MR stripe cause proportional changesin potential across the stripe. These potential changes are thenprocessed to produce playback signals corresponding to data signalsstored on the magnetic tape. It is important that the MR sensor beconstructed with predetermined conductivity to satisfy the design of thechannel electronics. Conductivity limits are exceeded when the MR sensoris constructed with too much or too little conductive material.

A typical type of MR sensor is an anisotropic MR (AMR) sensor. Thetransfer function of the AMR sensor varies by cos² α, where α denotesthe angle between a magnetization direction and a current-densityvector. The transfer function is a plot of the resistance change of theMR sensor as a function of the strength of an applied field signal fromthe tape, and can be shown as a curve (transfer curve) on a graph. Whenthe direction of the magnetic moment of the MR stripe and the directionof the sense current in the MR sensor are parallel, the MR stripe hasmaximum resistance; when these directions are perpendicular, the MRstripe has minimum resistance. It is desirable that an AMR sensoroperate within a linear portion of a bell-shaped transfer curve. This isaccomplished by appropriately positioning the direction of the magneticmoment of the MR stripe 45° to a plane of the head surface. Assumingthat positive and negative field signals from the moving magnetic tapeare equal, then each of the clockwise and counterclockwise rotations ofthe magnetic moment, the positive and negative changes inmagnetoresistance of the MR stripe, and the positive and negative signalresponses will be equal.

One way to bias the magnetic moment of the MR stripe at 45° is toprovide the MR sensor with a soft adjacent layer (SAL) adjacent to theMR stripe, but separated therefrom by an insulation layer. When thesense current is conducted through the MR stripe, a transverse field isapplied to the SAL and the SAL, in turn, applies a transverse field tothe MR stripe which rotates the magnetic moment of the MR stripe to the45° angle.

Another way to obtain the desired bias angle is to employ shapeanisotropy to establish the direction of the magnetic moment of the MRstripe along the desired bias angle. This scheme is employed by achevron type MR sensor which consists essentially of only the MR stripe.The chevron type MR sensor has a plurality of elongated ridges that areuniformly spaced from one another. Between the ridges are elongatedtrenches. These ridges and trenches are slanted to the plane of the headsurface by some angle, such as 45°. This arrangement has the appearanceof multiple chevrons, as seen in cross-section, such as a head surfaceview. The result is that the easy axis of the MR stripe is establishedalong the angle of the chevron structure or close thereto instead ofbeing parallel to the head surface. A SAL is not employed in thisscheme. When sense current is conducted through the MR stripe, thecurrent is directed parallel to the head surface and the magnetic momentis directed at substantially 45° to the head surface. This provides theaforementioned desirable bias angle for the operation of the MR sensor.

Typically, an MR sensor has first and second surfaces that areperpendicular to the head surface. Each of the first and second surfacesis configured with the ridges to provide a ribbed structure. The ridgeson the first surface are positioned opposite the trenches on the secondsurface and the ridges on the second surface are positioned opposite thetrenches on the first surface. Between the ridge structures, anintermediate portion of the MR sensor connects the ridges together.

Each ridge is bounded by first and second side walls, a flat surface atthe top of the ridge and the intermediate portion. Each trench between arespective pair of ridges is bounded by the side walls of the ridges anda flat surface at the bottom of the trench. In order to promote anorderly shape anisotropy of the MR sensor it is necessary that the sidewalls be planar and perpendicular to the flat surfaces of the ridges andthe side walls. As stated hereinabove, the MR sensor is sandwichedbetween the first and second gap layers. These layers are typicallyconstructed of alumina (AL₂O₃). Accordingly, the ridges and trenches ofthe first surface of the MR sensor interfacially engage trenches andridges respectively in the first gap layer and the ridges and trenchesof the second surface of the MR sensor interfacially engage trenches andridges of the second gap layer.

The present method of making the chevron type MR sensor typicallyresults in poorly formed chevron structures. First a photoresist mask isspun on the first gap layer and patterned by light followed bydissolving the exposed portions to provide elongated spaced apartopenings that are slanted at the appropriate angle to the head surface.Next, ion beam milling is employed to mill elongated trenches in thefirst gap layer that are spaced apart by non-milled elongated topsurfaces therebetween. These trenches and surfaces are slanted to thehead surface. The photoresist layer is then removed and MR material issputtered into the trenches and on top of the top surfaces. Thisprovides each of the first and second surfaces of the MR sensor with thechevron structure. The second gap layer is then deposited on the chevronstructure of the second surface of the MR sensor.

Unfortunately, the step of ion milling the first gap layer results inthe first gap layer having poorly formed side walls, unreliable depthsand fencing. The side walls have various slopes with respect to the topsurfaces of the first gap layer, the depths are too deep uponovermilling. or too shallow upon undermilling, and fencing is caused byredeposition of the milled material (redep) on the side walls. Since theredep typically sticks up above the side wall it appears as a fence.Next, during the step of depositing the MR material, the MR materialreplicates the shape of the first gap layer and has sloping side walls,bottoms that are too deep or too shallow and fencing. The manufacturingyield has been extremely low with the present method because of processvariations in the amount of conductive material in the chevron shaped MRsensor. As stated hereinabove, the amount of conductive material must beprecise to satisfy the requirements of the channel electronics.Accordingly, there is a strong felt need to provide an improved methodof making chevron structures for AMR read heads.

SUMMARY OF THE INVENTION

The present invention provides a method of making a well-defined chevronMR sensor with virtually no process variation. The first step is toselect a first material for the first gap layer that is not etched by aselected reactive ion etch (RIE) and to select a second material that isetchable by the RIE. Both the first and second materials must benon-magnetic and non-conductive. A layer of the second material is thenformed on the first gap layer. The thickness of the second materiallayer is chosen to be equal to a desired depth of the chevron structure.A photoresist layer is then spun on the second material layer andphotopatterned to provide elongated openings that are slanted at anacute angle to the head surface and that expose elongated top surfaceportions of the second material layer. The RIE is then employed to etchthe exposed top surface portions of the second material layer. The RIEwill etch through the thickness of the second material layer until itreaches the top of the first gap layer. Since the first gap layer cannotbe etched by the RIE material, removal is terminated. Exact depthcontrol (the thickness of the second material layer) is obtained eventhough the duration of the RIE exceeds that required to mill thethickness of second material layer. The importance of this result willbecome evident after describing the next steps of the process.

Next, the photoresist mask is removed, leaving elongated rectangularstrips of second material that are separated by elongated flat surfacesof the first gap layer. The strips are slanted at the acute angle to thehead surface and have first and second planar side walls that areinterconnected by a top planar surface. The first and second side wallsare perpendicular to the top surface of each strip. This is importantfor producing a well-defined chevron structure, which will becomeevident from the next step of the process.

Next, MR material is sputtered on the top surfaces of the strips and onthe elongated flat surfaces of the first gap layer between the strips.This forms an MR structure that has spaced apart ridges of MR materialon first and second surfaces of the MR structure, with trenchestherebetween. The ridges on the first surface are opposite trenches onthe second surface, and the ridges on the second surface are oppositetrenches on the first surface. Since the first surface ridges are formedby the first material strips and the elongated flat surfaces of thefirst gap layer therebetween, they have first and second side walls thatare perpendicular to a bottom planar surface. The second surface ridgesthat are sputtered on the top planar surface of the second materiallayer likewise have first and second side walls that perpendicular to atop planar surface. Each of the trenches between the ridges have firstand second planar side walls that are perpendicular to a bottom planarsurface of each trench. As a result, the MR sensor appears incross-section as a sawtooth curve with squared-off ridges that arelocated opposite squared-off trenches. Continuation of making the MRhead comprises forming a second gap layer on the second surface of theMR sensor. The second gap layer will cover the second surface of the MRsensor filling in the trenches of the chevron structure thereon. Thepresent process has eliminated the step of milling the first gap layer,which causes the aforementioned problems of depth control, sloping sidewalls and redep.

An example of materials for the first gap layer and the second materiallayer are Al₂O₃ and SiO₂ and an example of the RIE is a RIE that isfluorine based. The product produced by the method is novel due to factthat a plurality of intermediate second material strips are sandwichedbetween the first gap layer and the MR sensor.

An object of the present invention is to provide a method of making achevron type MR sensor which is square cornered.

Another object is to provide a method of making a chevron type MR sensorwith substantially no process variation.

A further object is to provide a method of making an MR sensor with achevron structure on each of first and second surfaces that is welldefined and has predictable configurations.

Still another object is to provide a method of making a chevron type MRsensor on a first gap layer wherein the first gap layer is not alteredby milling.

Still a further object is to provide a method of making a chevron MRsensor with exact depth control.

Still another object is to provide a method of making a chevron type MRsensor that predictably satisfies the design parameters of channelelectronics.

Still a further object is to provide a novel MR sensor that haselongated strips of nonmagnetic material sandwiched between a planarfirst gap layer and a chevron type MR sensor.

Other objects and advantages of the invention will become apparent uponreading the following description taken together with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of an exemplary magnetic tape driveemploying the magnetic head assembly of the present invention;

FIG. 2 is a view taken along plane II—II of FIG. 1 showing alongitudinal cross-sectional view of a combined read and write head;

FIG. 3 is a view taken along plane III—III showing a head surface of thecombined read and write head;

FIG. 4 is a view taken along plane IV—IV showing the top of the writehead portion with an overcoat layer removed to show a write coil withfirst and second leads and a second pole piece of the write head;

FIG. 5 is a view taken along plane V—V of FIG. 3 showing a prior artchevron type MR sensor of the read head;

FIG. 6 is a view taken along plane VI—VI of FIG. 5 showing a headsurface view of the read head with a prior art chevron type MR sensor;

FIG. 7 shows a first step in a prior art method of making a chevron typeMR sensor wherein a first gap layer is deposited;

FIG. 8 shows a second step in the prior art method of forming a resistframe on the first gap layer;

FIG. 9 is a third step in the prior art method employing ion milling tomill away portions of the first gap layer unprotected by the photoresistframe;

FIG. 10 is a fourth step in the prior art method of removing the resistframe;

FIG. 11 is a fifth step in the prior art method of forming a chevronconfigured MR sensor on the first gap layer;

FIG. 12 is the same as FIG. 11 except a second gap layer has beendeposited thereon;

FIG. 13 is a view taken along plane XII—XII of FIG. 3 showing thepresent chevron type MR sensor;

FIG. 14 is a view taken along plane XIII—XIII of FIG. 13 showing an ABSview of the present read head;

FIG. 15 shows a first step of the present method wherein a non-etchablefirst gap layer is deposited;

FIG. 16 is a second step of the present method of depositing a layer ofetchable material on the first gap layer;

FIG. 17 is a third step of the present method wherein a photoresistframe is formed on the first gap layer;

FIG. 18 is a fourth step of the present method wherein reactive ionetching (RIE) is employed to mill away unprotected portions of theetchable layer down to the first gap layer which is not etchable by theRAE;

FIG. 19 is a fifth step of the present method wherein the resist frameis removed;

FIG. 20 is a sixth step of the present method showing deposition of MRmaterial in the spaces between the etchable material and on top thereofto form the chevron shaped MR sensor; and

FIG. 21 is the same as FIG. 20 showing formation of a second gap layeron top of the chevron shaped MR sensor.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings wherein like reference numerals designatelike or similar parts throughout the several views, there is illustratedin FIG. 1 a magnetic tape drive 20 which includes a combined read/writehead 22 that is mounted on a support 24. The magnetic tape 26 is movedlinearly past a planar surfaces 28 of the support 24 and head 22 ineither a forward or reverse direction by a pair of reels 30 and 32. Adrive control 34 is provided for rotating the. reels 30 and 32alternately in the forward and reverse directions. The reels 30 and 32may be open or one or more of the reels may be mounted in a cartridge.When a cartridge is employed the magnetic tape is usually pulled fromthe cartridge by a leader pin which interlocks with a leader blockwithin the cartridge.

The support 24 is mounted on a movable support 36 so that the combinedmagnetic head 22 can be supported in a transducing relationship withrespect to the magnetic tape 26. The movable support 36 moves transverseto the magnetic tape 26 so that read and write heads of the combinedhead 22 can read and write magnetic information signals on thelongitudinally moving tape 26. The read head of the combined magnetichead 22 may be employed for reading servo tracks on the tape so as tokeep the read and write heads within a desired track. With thisarrangement, the combined magnetic head 22 feeds servo information to atrack control 38 which processes this information and feeds headmovement signals to the movable support 36. Further, the magnetic headsof the combined head 22 are connected to a data control 40 whichprocesses signals from the read head and to write head.

FIG. 2 is a side cross-sectional elevation view of the combined magnetichead 22 which has a write head portion 70 and a read head portion 72,the read head portion employing a chevron type magnetoresistive (MR)sensor 74 of the present invention. FIG. 3 is a head surface view ofFIG. 2. The MR sensor 74 is sandwiched between first and second gaplayers 76 and 78 and the gap layers are sandwiched between first andsecond shield layers 80 and 82. In response to external magnetic fields,the resistance of the MR sensor 74 changes. A sense current I_(s)conducted through the sensor causes these resistance changes to bemanifested as potential changes. These potential changes are thenprocessed by the data control 40 shown in FIG. 1.

The write head portion 70 includes a coil layer 84 sandwiched betweenfirst and second insulation layers 86 and 88. A third insulation layer90 may be employed for planarizing the head to eliminate ripples in thesecond insulation layer caused by the coil layer 84. The first, secondand third insulation layers are referred to in the art as an “insulationstack”. The coil layer 84 and the first, second and third insulationlayers 86, 88 and 90 are sandwiched between first and second pole piecelayers 92 and 94. The first and second pole piece layers 92 and 94 aremagnetically coupled at a back gap 96 and have first and second poletips 98 and 100 which are separated by a write gap layer 102 at the headsurface 28.

FIGS. 5 and 6 illustrate a read head 200 which includes a prior artchevron type MR sensor 202. As shown in FIG. 6 the NR sensor 202 hasfirst and second surfaces 204 and 206 wherein each of these surfaces hasa ribbed shape structure. As shown in FIGS. 5 and 6, the first surface204 of the MR sensor has a plurality of ridges 208 and a plurality oftrenches 210 which are arranged in an alternate fashion at an acuteangle, such as 45°, to a head surface 212. The second surface 206 of theMR sensor has complementary ridges 214 and trenches 216 which arearranged similarly in an alternate fashion with the ridges 208 of thefirst surface being opposite the trenches 216 of the second surface. Afirst gap layer 218 has alternating ridges 220 and trenches 222 whichhas been filled in the MR region with MR material. As shown in FIG. 5,first and second leads 224 and 226 are connected to the ends of the MRsensor for conducting a sense current I_(S) therethrough. The MRmaterial between the leads 224 and 226 is the active region of the MRsensor and defines the track width of the MR read head. A second gaplayer 228 is placed on top of the first gap layer 218 and the chevron MRsensor 202. The first and second gap layers 218 and 228 are sandwichedbetween first and second shield layers 230 and 232. The prior artchevron MR sensor 202 is constructed by a prior art method which resultsin poorly formed side walls, fencing and imprecise depth control of thetrenches 210 and 216.

The prior art method for making the chevron MR sensor 202 of FIGS. 5 and6 is shown in FIGS. 7-12. In FIG. 7 the first gap layer 218, which istypically AL₂O₃, is formed on the first shield layer 230 (see FIG. 6) byany suitable means such as sputtering. Next, a photoresist frame isformed on the surface of the first gap layer with a plurality ofphotoresist strips 234 that are separated by open spaces 236. Thephotoresist strips 234 and the open spaces 236 are elongated and areslanted at the aforementioned angle to the head surface. The open spaces236 expose surface portions 238 of the first gap layer. Next. ionmilling is employed, as shown in FIG. 9, to mill the exposed surfaces238 of the first gap layer to form elongated spaced apart trenches 240in the first gap layer that are slanted at an angle to the head surface.Next, the photoresist frame is removed leaving the first gap layer withits trenches 240, as shown in FIG. 10. Unfortunately, the ion millingcauses a considerable amount of redeposition (redep) of the AL₂O₃material onto the side walls causing the trenches to have inwardlysloping surfaces. Further, the redep causes fencing 242 which appears asspikes in cross-section, as shown in FIG. 10. Further, there has been noprecise depth control of the bottoms 244 of the trenches due to processvariations in the ion milling step.

Next, MR material is deposited on the first gap layer by any suitablemeans such as sputtering, as shown in FIG. 11. The result is that the MRmaterial replicates the configuration of the first gap layer causing theridges 208 and 214 and trenches 210 and 216 of the MR material to havesloped side walls. Further, the ridges 214 have fencing at 246 and thereis imprecise depth control of the MR structure within the trenches. Thiscauses an imprecise amount of MR material for conductivity whichsignificantly reduces a manufacturing yield because of a failure tosatisfactorily meet the design requirements of the channel electronics,which is encompassed in the data control 40 shown in FIG. 1.Accordingly, there is a strong-felt need to improve the process ofmaking the chevron MR structure so as to improve this yield and theperformance of chevron type magnetic read heads.

A novel read head 300 is shown in FIGS. 13 and 14 which employs thepresent chevron type MR sensor 302. As shown in FIG. 14, the MR sensor302 has first and second surfaces 304 and 306. The first surface hasinverted elongated ridges 308 and inverted elongated trenches 310 thatalternate with respect to one another and that are slanted at theaforementioned angle to the head surface 312. In a like manner, thesecond surface 306 has ridges 314 and trenches 316 that alternate withrespect to one another and that slant at the aforementioned angle to thehead surface 312. Further, the ridges 308 of the first surface arepositioned opposite the trenches 316 of the second surface and theridges 314 of the second surface are positioned opposite trenches 310 ofthe first surface. The present MR read head 300 (FIGS. 13 and 14)differs from the prior art read head 200 (FIGS. 5 and 6) in that thepresent MR read head has second material strips 320 which are of adifferent material than the material of the first gap layer 318, whichwill be explained in more detail hereinafter. The first gap layer 318 inFIG. 14 has not been milled to form trenches, which trenches are shownfilled with MR material in the prior art head 200 in FIG. 6. Othersignificant differences of the present MR head 300 is that the sidewalls of the ridges 308 and 314 and the side walls of the trenches 310and 316 are planar and are perpendicular to planar top surfaces of theridges and planar bottom surfaces of the trenches, which will beexplained in more detail hereinafter. Further, the present MR sensor 302does not have fencing since there is no redep of material which wascaused by ion milling the first gap layer in the prior art method. Asshown in FIG. 13, first and second leads 324 and 326 are connected toend portions of the MR sensor 302, thereby defining an active MR regiontherebetween. The MR sensor 302 is sandwiched between first and secondgap layers 318 and 328 and the first and second gap layers aresandwiched between first and second shield layers 330 and 332.

The method of making the present MR sensor 302 and head 300 is shown inFIGS. 15-21. In FIG. 15 the first gap layer 318 is deposited on thefirst shield layer 330 of FIG. 14 by any suitable means such as sputterdeposition. The first gap layer 318 is made of a first selectedmaterial, such as AL₂O₃. The next step is to deposit a second materiallayer 340 made of a second selected material by any suitable means, suchas sputter deposition. An example of the material for the secondmaterial layer 340 is SiO₂. Next, a resist frame 342 is formed whichcomprises elongated resist strips 344 and openings 346 which arealternately arranged and slanted at the aforementioned angle to the headsurface of the magnetic head. The openings 346 expose top surfaceportions 348 of the second material layer 340.

The next step is to employ a selected reactive ion etch (RIE) which, byway of example, is fluorine based which is represented as RIE_(F). It isimportant that the material of the second material layer 340 be etchableby the RIE_(F) and that the material of the first gap layer 318 be notetchable by the RIE_(F). In the examples given, the SiO₂ material of thesecond material layer 340 is etchable by the RIE_(F) and the AL₂O₃material of the first gap layer 318 is not etchable by the RIE_(F). Thisis important from the standpoint that, even though the RIE_(F) hasetched for a duration longer than that necessary to completely mill awaythe exposed portions 348 of the second material layer 340, the RIE_(F)will not mill into the AL₂O₃ material of the first gap layer 318. Thisprovides for precise depth control of the MR structure to besubsequently formed. The next step is to remove the resist frame, asshown in FIG. 19. This leaves the aforementioned second material strips320 wherein each strip 320 is bounded by the first gap layer 318, firstand second side walls 350 and 352 and a top surface 354 which are allplanar and perpendicular with respect to one another. Accordingly, eachstrip 320 has square comers and does not have any fencing which is aserious detriment resulting from the prior art method. It should benoted that at this point there has been no milling of the first gaplayer 318 which specifically distinguishes the present method over theprior art method.

Next, MR material is formed on the first gap layer 318 and the strips320 by any suitable means, such as sputter deposition. The MR materialwill replicate the strips 320 and the spaces 322 therebetween to form achevron type MR sensor 302 that has the first and second surfaces 304and 306 with ridges 308/314 and trenches 310/316, respectively. The MRmaterial is deposited to a sufficient thickness so that the MR sensorhas an intermediate portion between the ridges 308 and 314 for tying thestructure together. It can be seen from FIG. 20 that the ridges 308 and314 have first and second vertically oriented planar side walls whichare perpendicular to horizontally extending flat surfaces. This resultsin the trenches 310 and 316 likewise having vertically oriented planarside walls which are perpendicular to horizontally extending flatsurfaces. Accordingly, the MR sensor 302 has square comers which doesnot have any fencing. Because of this and precise depth control thepresent MR sensor can easily satisfy the design requirements of channelelectronics, thereby promoting a high manufacturing yield. As shown inFIG. 21, the second gap layer 328 is deposited on the MR sensor 302 byany suitable means, such as sputtering. This causes the second gap layerto conform to the shape of the MR sensor 302.

In the broad aspect of this invention the second material layer is astable oxide, such as SiO₂, SiO, SiON, SiN and Ta₂O₅. In a more narrowaspect of the invention the second material layer is silicon-based. Inthe preferred embodiment, the second material layer is SiO₂. In a broadconcept of the invention, the material of the gap layer is Al₂O₃ or apolyimide. In a preferred embodiment the material of the first gap layeris Al₂O₃. In a broader concept of the invention the fluorine base of theRIE is CF₄, SF₆, or CHF₃. In a preferred embodiment the base of the RIEis CF₄. Accordingly, a preferred embodiment of the invention is SiO₂ forthe second material layer, Al₂O₃ for the material of the first gap layerand a RIE that has CF₄ base. It should be understood that the RIE takesplace in a chamber where the plasma in the chamber contains the fluorinebased gas such as CF₄. The partially completed head is part of an anodein the chamber and a cathode in the chamber provides a stream ofelectrons directed toward the partially completed head to remove theexposed portions of the SiO₂. The fluorine base provides the necessarychemical etching for removing the exposed portions of the secondmaterial layer with great selectivity, and yet without any danger ofmilling into the first material of the first gap layer 318. The resultis a highly-defined predictable MR sensor which substantially increasesthe manufacturing yield.

Clearly, other embodiments and modifications of this invention willoccur readily to those of ordinary skill in the art in view of theseteachings. Therefore, this invention is to be limited only by thefollowing claims, which include all such embodiments and modificationswhen viewed in conjunction with the above specification and accompanyingdrawings.

We claim:
 1. A method of making a magnetoresistive (MR) head that has aMR sensor sandwiched between first and second gap layers, each of the MRsensor and the first and second gap layers having first and secondsurfaces that face in opposite directions and are substantiallyperpendicular to a head surface, the first surface of the MR sensorinterfacially engaging the second surface of the first gap layer and thesecond surface of the MR sensor interfacially engaging the first surfaceof the second gap layer, the method comprising: forming the first gaplayer of a first material that is resistant to a reactive ion etch(RIE); forming an etchable layer of a second material on the secondsurface of the first gap layer, the etchable layer being etchable bysaid reactive ion etch (RIE); forming a mask on a second surface of theetchable layer with a plurality of alternating elongated ridges andelongated spaces; the ridges and spaces of the mask having longitudinalaxes that are parallel with respect to one another and that slant at anangle θ between 0° and 90° with respect to said head surface and thespaces exposing spaced apart elongated surface portions of the etchablelayer; etching the exposed surface portions of the etchable layer withsaid RIE down to said first gap layer to form alternating elongatedridges and elongated spaces in the etchable layer that are substantiallyparallel with respect to one another and slanted at said angle θ to saidhead surface; removing the mask; depositing ferromagnetic material onthe ridges and in the spaces of the etchable layer to form said chevrontype MR sensor; and forming said second gap layer on the chevron type MRsensor.
 2. A method as claimed in claim 1 wherein the second material isa stable oxide.
 3. A method as claimed in claim 1 wherein the RIE isfluorine based.
 4. A method as claimed in claim 1 wherein said firstmaterial is alumina or polyimide.
 5. A method as claimed in claim 1wherein the spaces of the etchable layer expose elongated surfaceportions of the first gap layer that are substantially parallel withrespect to one another and are slanted at said angle θ to said headsurface.
 6. A method as claimed in claim 1 wherein the first materialcomprises Al₂O₃, the second material comprises SiO₂ and the RIEcomprises RIE_(F).
 7. A method as claimed in claim 1 wherein the firstgap layer, the etchable layer and the MR sensor are formed by sputterdeposition.
 8. A method as claimed in claim 1 wherein said depositingforms: each surface of the MR sensor with alternating elongated ridgesand elongated trenches that are parallel with respect to one another;the ridges of the first surface being located opposite the trenches ofthe second surface and the ridges of the second surface being locatedopposite the trenches of the first surface; and the MR sensor with anintermediate portion that is integral with the ridges of the first andsecond surfaces of the MR sensor and surface portions that form bottomsof the trenches of the first and second surfaces of the MR sensor.
 9. Amethod as claimed in claim 8 wherein the second material is a stableoxide.
 10. A method as claimed in claim 9 wherein the RIE is fluorinebased.
 11. A method as claimed in claim 10 wherein said first materialis alumina or polyimide.
 12. A method as claimed in claim 11 wherein thespaces of the etchable layer expose elongated surface portions of thefirst gap layer that are substantially parallel with respect to oneanother and are slanted at said angle θ to said head surface.
 13. Amethod as claimed in claim 12 including: said mask being photoresist;and the first gap layer, the etchable layer and the MR sensor beingformed by sputter deposition.
 14. A method as claimed in claim 13wherein the second material is selected from the group containing SiO₂,SiO, SiON, SiN and Ta₂O₅.
 15. A method as claimed in claim 14 whereinthe fluorine is selected from the group containing CF₄, SF₆ and CHF₃.16. A method as claimed in claim 15 wherein the first material comprisesAl₂O₃, the second material comprises SiO₂ and the RIE comprises RIE_(F).